2019ApJ...879..123L

We present a detailed study of the optical and near-infrared (NIR) emission and absorption line spectrum of the quasar SDSS J163345.22+512748.4. We discovered on the newly acquired NIR spectrum a highly metastable neutral helium broad absorption line (BAL) He I* λ10830 with a width of ∼2000 km s^–1 and a blueshift of ∼7000 km s^–1 in the velocity space. The BAL system is also significantly detected in Mg II and He I* λ3889. We estimate a column density of (5.0 ± 1.7) x 10¹⁴ cm^–2 for the He I*(2 ³S) level and infer an ionization parameter of U_A = 10^–1.9±0.2 for the BAL outflow, assuming that the BAL region is thick enough for a full development of an ionization front. The total column density of the BAL outflow is constrained in the range N_H ∼ 10²¹-10^21.4 cm^–2. We also found that the bulk of both Mg II and UV Fe II, as well as of Hα broad emission lines (BELs), are blueshifted with a velocity of ∼2200 km s^–1 with respect to the quasar systemic redshift. We constrain the blueshifted BEL region to have a covering factor C_f ≃ 16%, density n_H ∼ 10^10.6-10^11.3 cm^–3, column density N_H >= 10²³ cm^–2, and ionization parameter U_E ∼ 10^–2.1-10^–1.5. The outflow gas is located at ∼0.1 pc away from the central ionization source, at a scale comparable to the broad-line region. A toy kinetic model has been proposed to reproduce the profile of Mg II BEL well if a partial obscured axisymmetric geometry of the outflow with a radial velocity as observed from the BALs is assumed.